The present invention is directed, in general, to power management for integrated circuits and, more specifically, to power management with electrostatic discharge latchup event recovery for fingerprint sensor devices.
Electrostatic discharge techniques normally employed for integrated circuits are often not entirely suitable or satisfactory for fingerprint sensor devices. Because such sensor devices must, of necessity, allow contact in proximity to the sensor circuitry, electrostatic discharge (ESD) protection to prevent latchup, circuit damage and other problems must be implemented in a different manner.
A primary requirement of power management for fingerprint sensor devices is the ability to restore operation of the fingerprint sensor circuitry following a latch-up condition triggered by an electrostatic discharge event. However, the same electrostatic discharge event occurring on the fingerprint sensor device and propagating inside the power management unit should not affect functionality of the power management unit.
Fingerprint sensor devices may be required to operate at a nominal 5V supply, although optional operation at 3.3 volts supply may also be desired. Whether the dual power supply voltage capability accomplished by a charge pump receiving 3.3 volts and generating the 5 volt power supply voltage level or by a power regulator running out of 5 volts to produce both voltage levels, the power management unit should control the power of the charge pump or power regulator, if present, as well as shutting down the power supply of the fingerprint sensor device at will.
There is, therefore, a need in the art for a power management system for fingerprint sensor devices which allows control over power to the fingerprint sensor device and enables recovery from electrostatic discharge events.
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide, for use in a fingerprint detection system, a power management unit which monitors current drawn by a fingerprint sensor circuit and generates a xe2x80x9cheartbeatxe2x80x9d signal during normal operation. If a latchup event occurs, with attendant increase in current drawn by the fingerprint sensor circuitry, the heartbeat signal terminates and an interrupt is subsequently triggered to start a latchup recovery routine. Power to the fingerprint sensor circuitry is switched off and the interrupt is then cleared by writing appropriate values to control bits within the power management register.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art will appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words or phrases used throughout this patent document: the terms xe2x80x9cincludexe2x80x9d and xe2x80x9ccomprise,xe2x80x9d as well as derivatives thereof, mean inclusion without limitation; the term xe2x80x9corxe2x80x9d is inclusive, meaning and/or; the phrases xe2x80x9cassociated withxe2x80x9d and xe2x80x9cassociated therewith,xe2x80x9d as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term xe2x80x9ccontrollerxe2x80x9d means any device, system or part thereof that controls at least one operation, whether such a device is implemented in hardware, firmware, software or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior as well as future uses of such defined words and phrases.